What size leveling feet

[682bear]

The manual for my lathe doesn't specify the size of the bolts to mount the lathe on the bed. Just says use supplied screws. My lathe weighs around 350 pounds. The motor and its mounting bracket is separate from the lathe. The lathe by itself probably weighs around 275 pounds. I can pick up either end of the lathe. My current mounting bolts are 7/16. All the bolts do is hold the lathe to the bench. Don't support the weight of the lathe. I think that 1/2 is the largest bolt that will fit through the mounting holes. I plan to make threaded washers (wrong term??) as thick as a standard size nut. Flange nuts would also work. The bolt will come up through the bench top. A threaded washer will be screwed down to hold the bolt in place. Another threaded washer will be screwed onto the bolt. The lathe will sit on this washer. Then there will be a nut that holds the lathe against the threaded washer. Move the threaded washer that the lathe sits on to remove any twist in the bed. Then tighten the nut to hold everything in place. That's the plan so far.

I would consider that to be a good plan...

-Bear

 

[akjeff]

With nothing pressing this afternoon I decided to research how much force is needed to strip the threads on nuts and bolts. . Did not find any tables on the force required to strip threads. One post I read referenced the proof load of nuts as the value at which a given nut size would strip. Didn't seem to matter whether the load on the nut was pushing the nut or pulling the nut. That should be easy to find. Not. After spending more time than I should have on this all I learned is that the calculations are mind boggling to a non engineer and that a standard size nut for a given bolt is stronger than the bolt. Bolts are referenced by tensile strength. There are charts for the tensile strength of bolts. A 1/4-20 has a tensile strength of 1750 lb. A 3/4-10 has a tensile strength of 15,200 lb. This a for a cheapy grade 2 bolt. The clamping force is 75% of the tensile strength.

As best as I can tell the bolts you guys are using are way overkill for the loads applied to the bolts. Now there may be other factors that I am unaware of the require larger bolts and nuts.

I did this because I am thinking of using nuts on threaded rod to level my lathe instead of shims.

Great info, but tensile strength is only part of the picture. For one, I would fill the hole with the largest fastener that will fit it, just to cut down on play/slop, and if you live in an area with even mild seismic activity, then there's shearing forces that may make what is "overkill" in a perfect world, become "sufficient". Even something as small as the bolt not being perfectly perpendicular to the load can derate it significantly. I'm a big fan of overkill.

 

[Aukai]

I got the 6 x 6 cut, and the leveling feet came, but no studs. I thought when I ordered it was included, I sent an email to find out.

 

[Al 1]

3000 lb. concrete should take 3000 lb. per square inch. Al.

 

[usamech]

Hmmm... so my all-thread, 1-1/8" diameter adjusters are a little over-kill for an 1100lb Clausing (first lathe) I have yet to get? I'm new to even being a novice, and can't wrap my head around how a 5/8" diameter bolt can support that much weight/mass, especially absorbing vibration, etc.?

I'll have to figure out how to put a good radius on the end and dish or dimple a pad for it to sit on. I press-pinned nuts on all-thread as bolt heads. I bet somebody here knows...., but it's too early to post that question since I don't even have it yet.

 

[WobblyHand]

Hmmm... so my all-thread, 1-1/8" diameter adjusters are a little over-kill for an 1100lb Clausing (first lathe) I have yet to get? I'm new to even being a novice, and can't wrap my head around how a 5/8" diameter bolt can support that much weight/mass, especially absorbing vibration, etc.?

I'll have to figure out how to put a good radius on the end and dish or dimple a pad for it to sit on. I press-pinned nuts on all-thread as bolt heads. I bet somebody here knows...., but it's too early to post that question since I don't even have it yet.

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When I asked the very same question, not all that long ago, I was advised to make an obtuse angle in the end of the bolt head and make a matching dimple in the plate. If I recall correctly I made a 140 degree angle. I was told not to bother with making a spherical end as there was no real benefit. I can report it works fine.

 

[NC Rick]

3000 lb. concrete should take 3000 lb. per square inch. Al.

What of vibration and time? Concrete thickness and soil conditions under it? I seem to have tiny crack webs all around my lathe. It is maybe 2500 lbs siting of 6, 2” diameter steel disks about 5/8” thick. I think about these things too much.

 

[rabler]

What of vibration and time? Concrete thickness and soil conditions under it? I seem to have tiny crack webs all around my lathe. It is maybe 2500 lbs siting of 6, 2” diameter steel disks about 5/8” thick. I think about these things too much.

One of my concerns is that I doubt steel on concrete is likely to give a uniform pressure distribution. Seems like a sheet of cheap self adhesive vinyl tile or similar may make a significant difference in that distribution and absorb some of the vibration without being too soft. I’m thinking about a couple of 8000lb machines in particular.